Chemistry Solids NUMS 2023
PMDC Verified Question 28 of 54
Which statement correctly describes the structure of sodium chloride crystal?
A
Each sodium ion is surrounded by six chloride ions and each chloride ions surrounded by 6 sodium ions
B
The crystal is face centered cubic structure
C
Each sodium ion is surrounded by 3 chloride ions and each chloride ion surrounded by sodium ions
D
Intermolecular forces are present between two oppositely charges ions
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: Each sodium ion is surrounded by six chloride ions and each chloride ions surrounded by 6 sodium ions
Concept:
The crystal structure of Sodium Chloride (\( \text{NaCl} \)) is defined by its highly ordered, face-centered cubic (FCC) lattice geometry.

Solution:
  • In the \( \text{NaCl} \) lattice, every \( \text{Na}^+ \) cation sits in an octahedral void created by the larger \( \text{Cl}^- \) anions.
  • This specific geometric arrangement dictates that exactly six chloride ions surround each sodium ion.
  • Because the lattice is perfectly symmetrical and infinite in 3D, the reverse is also true: each chloride ion is surrounded by exactly six sodium ions.
  • Thus, it has a 6:6 coordination ratio.


Why other options are incorrect:
  • C: A 3-ion coordination is incorrect; it is a 6:6 ratio.
  • D: The forces between oppositely charged ions are strong, intramolecular electrostatic ionic bonds, not weak intermolecular forces.
  • B: While \( \text{NaCl} \) is FCC, Option A provides the most complete and specific functional description of the ionic interactions in the structure. (Note: Option A is recognized as the best, most comprehensive answer in standard MCQ keys).

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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